JPS5937658B2 - Method for improving iron loss in stators of large rotating electric machines - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for improving iron loss in a stator of a large rotating electric machine using a unidirectional electrical steel sheet.

Unidirectional electrical steel sheets are examples of electrical steel sheets with excellent magnetic properties;
The surface is parallel to the rolling surface, and magnetization is easy in the rolling direction, that is, the length direction of the steel strip, but it is not easy to magnetize in the width direction because it is the (110) axis.

The stator and rotor of rotating electric machines such as electric motors and generators generally use a laminated core, and each core element of a predetermined shape is punched out of a steel plate, stacked to a predetermined thickness, and bundled. The rotor has a circular shape with many teeth on the outer circumferential surface, and the stator has a circular shape with many teeth on the inner circumferential surface.The magnetic flux flows in the radial direction (radial direction) at the teeth and in the circular direction at the yoke. Passes in the circumferential direction.

In other words, the magnetic flux does not pass in one direction, but in any direction over 360°, which makes it difficult to use grain-oriented electrical steel sheets for rotating machine cores. Conventionally, non-oriented electrical steel sheets have been used for this purpose. It was common.

However, for large rotating machines, the size of the annular stator core element is too large to be punched directly from a steel plate, so the fan-shaped core element is divided into multiple parts and then punched out from the steel plate. Laminated on the stator.

In this case, the yoke or teeth of the fan-shaped core element can be aligned in the rolling direction, so unidirectional electrical steel sheets can be used, and are actually used.

However, (7) In this case as well, if the yoke section is aligned with the rolling direction, the magnetic flux direction at the tooth section will be the (110) axial direction, and if the tooth section is aligned with the rolling force direction, the magnetic flux direction at the yoke section will be the [110] axial force. Turning towards
In either case, inconvenience will occur.

This section aims to solve these problems metallurgically.
Although bidirectional electrical steel sheets and the like have been developed, they are not in a state where they can be mass-produced at low cost.

The present invention attempts to improve this problem by a so-called physical method, and will be described in detail below with reference to the drawings.

As mentioned above, the unidirectional electrical steel sheet is (110) (001)
It has a structure and is easily magnetized in the rolling direction.

The rolling direction F is as shown in FIG.
When pulsed laser light is irradiated in a linear array such as a line, a chain line, or a dotted line substantially perpendicular to the line (12 indicates the irradiated portion in the case of linear irradiation), iron loss is reduced.

This can be explained as follows. That is, unidirectional electrical steel sheet 1
0 has a relatively large magnetic domain 14 extending in the rolling direction, as shown in FIG. 2a.

In grain-oriented electrical steel sheets, the number of crystals increases as the degree of concentration of (110)[:001) force potential in the rolling direction increases, and the magnetic domain becomes larger because the domain wall penetrates the grain boundary. Since there is a proportional relationship between iron loss and iron loss value,
There is a paradoxical problem in that the iron loss does not decrease as the directionality increases.

On the other hand, when the laser beam is irradiated in a direction substantially perpendicular to the rolling force direction, small protrusions 16 are generated on both sides of the irradiated portion 12.

This can be observed using a scanning electron microscope or the like.

Note that in the figure, only a portion of the small protrusions are shown for simplicity.

These small protrusions are buds of magnetic domains, and when magnetized, the magnetic domains 14 of the steel sheet 10 are subdivided by magnetic domains 18 extending from these buds.

Therefore, iron loss becomes small.

It is thought that the small protrusions 16 are generated because dislocations occur when the steel plate 10 is irradiated with a pulsed laser, and the probability of occurrence of magnetic domain buds is proportional to the density of these dislocations.

When the laser beam is irradiated in the rolling direction as shown in FIG. 1, small protrusions 16 are also generated as shown in FIG. 2.

It is thought that when an external magnetic field H acts, microdomains are generated from this bud 16, which lowers the iron loss.

To give a specific example, as shown in Figure 1a, the iron loss WL in the rolling force direction (magnetic flux density 1.7T, frequency 5
0Hz) is ],, 00 W/kg, and the iron loss Wc in the direction perpendicular to the rolling force direction (magnetic flux density 1.3T, frequency 50H
z) is almost the same as that without laser beam irradiation.

In addition, wL before laser beam irradiation is 1.10'W/
kg, Wc is 2.84W/kg.

In other words, the laser beam irradiation shown in FIG. 1a allows a 10% reduction in WL.

In the case of Figure 1, WL hardly changes and Wc is 2.04.
W/kg, making it possible to significantly reduce Wc by approximately 28%.

In order to obtain such an effect, conditions are met for laser beam irradiation, first of all, the width d and pitch l of the laser beam irradiated portion 12, in the case of FIG. 1 to 1~
20m7rL1 The time width of the laser pulse is 1 nS-
100ms is good.

The energy density P is preferably 0.01 to 1oooJ, /=.

In addition, when irradiating pulsed laser light, when the irradiated parts are arranged in a chain line or dotted line, the diameter d in the L direction is 0.01 to 1 mm in FIG. , preferably 1 mrn or less.

Also, in Figure 1, the diameter in the C direction d = 0.01 to 11111
1L, the directional spacing a between the irradiation points must be 3r/lT/L or less, preferably Lmvt or less.

Fig. 1 a, t) Even if the direction of the co-laser beam irradiation portion 12 is not aligned at right angles and parallel to the direction of rolling force, it will not be effective as long as it deviates within a range of ±30°. There is no particular difference.

Therefore, in the present invention, the steel plate elements constituting the fixed core of a large rotating machine with a split stator structure are irradiated with the above-mentioned laser beam to reduce the iron loss in the portion where the magnetic flux passes in a direction approximately perpendicular to the rolling force direction. The aim is to further reduce the iron loss in the portion where the iron passes in the rolling direction.

Figure 3a shows the procedure for punching a stator core from a unidirectional electrical steel sheet (rolling direction is F) 10, 20 is a fan-shaped stator core element, 20b is a tooth thereof, and 20a is a yoke. It is.

The width W of the unidirectional electrical steel sheet 10 is about 1 m, and in order to extract the iron core element 20 from the steel sheet 10 with less waste,
Adjacent core elements 20', 20// may be oriented in opposite directions.

The longitudinal direction F1 of the iron core element 20 is aligned with the rolling force direction F of the steel plate 10.

Here, it is assumed that the longitudinal direction F1 is a direction perpendicular to the radial direction R1 at the center of the fan-shaped element 20.

As shown by the dotted line in Figure 3, the magnetic flux in the core element is in the circumferential direction F2 at the yoke, in the radial direction at the tooth, and in the arc shape connecting these at the boundary between the yoke and the tooth. If three-phase excitation is used, it will be an arc shape that bends to the left or right depending on the current phase at each point in time.

Therefore, regarding the yoke part, if the magnetic flux direction is aligned with the rolling force direction at the center of the fan-shaped element 20, the magnetic flux direction (original) at the left and right ends will deviate from the rolling force direction, that is, the direction of the easy-to-magnetize (Cool) axial force, and this The angle of deviation varies depending on the number of divisions of the stator, but is usually 20 to 30 degrees.

In addition, in the tooth portion 20b, if the longitudinal direction F1 of the fan-shaped element is aligned with the rolling force direction F, the magnetic flux direction of the tooth portion at the center of the fan-shaped element becomes a direction perpendicular to the rolling force direction, and the magnetic flux direction at the left and right end portions of the fan-shaped element is It will be shifted by 20 to 30 degrees.

In unidirectional electrical steel sheets, increasing the degree of integration of the (110) ['0O1) structure in the rolling direction can significantly improve iron loss. This 20~30° has a great effect on iron loss.
The misalignment is also a problem that cannot be ignored.

Moreover, in the teeth, the magnetic flux is perpendicular to the [001] axis [11
0] Axis, that is, magnetization passes in a direction that is difficult, and furthermore, at the boundary between the teeth and the yoke, magnetization passes in the (111) direction, which is difficult to achieve. This is a reason to give up on application.

Therefore, in the present invention, a third
Pulsed laser light is irradiated as shown in the striped pattern shown in the figure.

That is, for the yoke part 20a of the element 20, the method shown in FIG.
The teeth 20 are irradiated with laser light so as to extend in the L direction (radial direction) and line up in the L direction (circumferential direction) with a pitch of a predetermined interval l.
In b, by adopting the method shown in Fig. 1, the laser beam irradiated portions 12 of a predetermined width d extend in the L direction (circumferential direction) and are lined up in the C direction (radial direction) with a pitch of a predetermined interval l. .

In order to create the laser beam irradiation portion 12, the pulsed laser beam may be sequentially deflected, that is, scanned, or the pulsed laser beam may be limited by a slit or the like and a narrow strip of pulsed laser beam that coincides with the portion 12 may be irradiated.

In the case of the latter pattern irradiation, a plurality of laser beam irradiation portions 12 may be projected simultaneously.

Even if the laser beam irradiated portion 12 of the tooth portion 20b is formed into a straight line instead of an arc, the deviation between the two is very small.

If the methods shown in FIGS. 1a and 1b are directly applied to this core element 20, all of the laser beam irradiated parts 12 in the yoke part 20a will extend in a direction parallel to the radius R1 at the center, and the fan-shaped end Then, a deviation of 20 to 30 degrees occurs from the above.

The same applies to the tooth portion 20b, and the laser beam irradiation portion 12 extends in a direction perpendicular to the radius R1 of the center of the fan-shaped element 20, that is, in parallel to the aforementioned longitudinal direction F1. This results in a deviation of ~30°.

However, this degree of deviation is permissible for the reasons mentioned above, and since this deviation corresponds to the direction of one electromagnetic flux, a rather favorable effect can be expected.

If the laser beam irradiation method for the tooth portion 20b is applied in a tapered manner to the boundary between the tooth portion 20b and the yoke portion 20a as shown in the figure, the magnetic flux is guided in the direction of the chain line, and as shown in FIGS.
The iron loss can be reduced for the reason explained in 2. However, the laser beam irradiation procedure for the yoke part as shown in Fig. 3C may be applied to this part, and the magnetic flux may be oriented in various directions. Since the quantity is small, it may be decided not to irradiate the laser as shown in FIG. 3d.

As explained above, according to the present invention, it is possible to improve the stator core loss in both the tooth portion and the yoke portion of a split stator type rotating electrical machine using unidirectional electrical steel sheets.

As is well known, iron loss occurs constantly during the operation of electrical equipment, and many large rotating electric machines operate continuously for long periods of time, so the energy saving effect of reducing iron loss is extremely large.

[Brief explanation of the drawing]

1A and 1B are diagrams for explaining the procedure of laser beam irradiation, FIGS. 2A and 2B are diagrams for explaining the reason for improving iron loss, and FIGS. 3A to 3D are diagrams for explaining the present invention in detail. In the drawing, 20 is a sector-shaped element of a split stator core, 10 is a unidirectional silicon steel plate, 20a is a yoke part, 20b is a tooth part, 12
is the part irradiated with laser light.

Claims (1)

[Claims] 1 Each fan-shaped element of the stator core divided into a plurality of pieces is punched from a unidirectional electromagnetic steel sheet with its longitudinal direction aligned with the rolling direction or a direction perpendicular to the rolling direction. A laser beam irradiation part of a predetermined width extends in the radial direction of the fan-shaped yoke part, and a laser beam irradiation part of a predetermined width extends in the tooth part in a direction almost parallel to the circumference, and the parts are arranged at a predetermined pitch in the circumferential and radial direction. A method for improving iron loss in a stator of a large rotating electric machine, which is characterized by irradiating a pulsed laser beam so that the